Effects of different liming rates on selected soil chemical properties and the vegetative growth of young oil palm on tropical peatlands

Tropical peat soils pose unique agronomic challenges due to their high acidity and low fertility. Liming with calcium carbonate (CaCO₃) is a common practice to improve soil pH and fertility; however, the substantial buffering capacity of peat soil complicates optimal lime application rates. Many studies focus on the effects of liming on soil pH and crop yield, but less is known about its wider impact on the chemical properties of tropical peat soils. This study evaluated lime effects through both a laboratory incubation and a 5.5-year field experiment to assess soil chemistry, nutrient dynamics, and young oil palm growth, while examining whether controlled-condition soil responses correspond with long-term field observations. The study includes lime rates: Control (L0), 3 t ha-1 (L1), 6 t ha-1 (L2) and 12 t ha-1 (L3). Under controlled conditions, lime application significantly increased soil pH from 3.2 to 7.5 (p < 0.05) and decreased cation exchange capacity (CEC) from 49.5 to 30.1 cmol kg-1 (p < 0.001). However, lime rates above 6 t ha⁻¹ did not further increase soil pH or reduce CEC, likely due to Ca²⁺ saturation of exchange sites and the strong buffering capacity of peat. Lime increased calcium (Ca) concentrations but decreased magnesium (Mg) and potassium (K), as Ca²⁺ displaced Mg²⁺ and K⁺ from exchange sites. Lime also significantly decreased net mineralization (p < 0.001), indicating nitrogen (N) immobilization. In the field trial, lime application significantly increased topsoil pH (3.50 to 4.00) and enhanced total Ca and Mg concentrations, while reducing exchangeable Al toxicity. However, CEC, soil organic matter (SOM) content, and electrical conductivity (EC) remained statistically unaffected. While vegetative growth parameters such as leaf area index (LAI) showed no significant changes, fruit bunch production increased significantly at moderate lime rates, indicating improved nutrient balance and reduced soil acidity. These findings highlight that lime application at moderate lime rates (6 t ha-1, L2) can effectively improve soil fertility and support yield performance without adversely affecting vegetative traits, offering practical guidance for oil palm cultivation on tropical peat.